“Several years ago, a scammer woke me up at 4 am. Some nonsense about me “owing to the IRS”. A few months later, some clueless telemarketer forgot about the existence of time zones and rang me up at 6 am. “It would be awesome to have a device that turns phone off during the night hours, then turns it back on during the day, all done automatically!” - was an obvious idea that popped into my mind. That was years before I have got myself interested in electronics. Yes, I am talking about the POTS (plain old telephone service, a.k.a. landline), since modern smartphones have this useful function built in. Now that I know a bit more about electronics and POTS in particular, I figured that turning the entire phone off is actually an overkill. I have built a circuit that achieves all of the following objectives: It prevents ringing of all the phones in the house that are on the same line, simultaneously; To the outside caller it just appears like nobody is picking the phone up. Otherwise, the circuit does not interfere with normal phone operations and calls can be made at any time. It is powered from the phone line itself. There are no other power sources. It is practically undetectable by the phone company, because it uses only a very small amount of power during its 6-minute startup, after which it enters a very low power mode using only 4 uA of current. If you already know all the basics of POTS signaling, or don’t care about the underlying principles, then you can skip the next step.”